Latest Mega Man 10 art hints at 3rd playable character

The latest piece of retro art for Mega Man 10 features Dr. Light, Mega Man and Proto Man in all there robotic glory. It also features the hand belonging to one unannounced character. The folks over at Capcom-Unity have hinted that this is the third playable character who shall be formally announced tomorrow.
This latest artwork only solidifies our assumption that Bass will be the third and final playable character. What other character has a black hand?

Feel free to leave your guesses as to who the final character will be in the comments section below.